First, some advice:

• LANDSCAPE ORIENTATION – over 90% of the time you should be shooting in Landscape orientation [a.k.a. SIDEWAYS]. The ONLY time Portrait Orientation is preferred is if 99% of your audience will be looking at the video on their phone, AND they don’t know how or are too lazy to turn their phone sideways.
• GOOD AUDIO IS IMPORTANT. After all, without it you just created a silent movie. Talk louder than you think, and be aware of all the noise that it around you [try closing your eyes and listening to the sounds around.]
• PLAN what is going to happen – it will save time. What shots do you want? What sounds? Where? Who is going to be in it?

Here’s a good process to follow when creating a video

• Shoot your footage.
• Get too much video – it’s easier to delete extra material than to stretch out material because you don’t have enough.
• Put the clips in rough order.
• Add titles.
• Record your voiceover, if you are going to add one.
  • After recording bump the volume up as much as you can – avoid a lot of red in the waveform, though a bit is usually OK. Your ears will tell you.
• Watch it 5 times – look for problem spots and fix them.
• Export the movie and send it on its way. Google Drive is a good place to stash video.

Some Online Help:

• How to record a voiceover:
  • https://www.bing.com/search?FORM=U523DF&PC=U523&q=IOS+iMovie+how+record+voiceover
• How to Edit Clips
  • https://www.bing.com/search?q=IOS+iMovie+how+edit+clips&qs=n&form=QBRE&sp=-1&pq=ios+imovie+how+edit+clips&sc=1-25&sk=&cvid=9714A9D533DF42CCB8C5C1638777A7EB
• How to Export your creation
  • https://www.bing.com/search?q=IOS+iMovie+how+export&qs=n&form=QBRE&sp=-1&pq=ios+imovie+how+export&sc=4-21&sk=&cvid=FA43C41EB78B4EE49434C7A428D5563C